little amount of light, that is scattered inelastically, submits part of its energy to phonons. Therefore,
by measuring the change in energy and momentum during inelastic Raman scattering one can measure
the phonon modes. The occupation of the phonon modes can be determined by comparing how many
photons are lifted to higher energy levels (anti-Stokes process) to how many photons are scattered to
lower energies (Stokes process).
(a) (b)Figure 19: a) Phonon dispersion relation for Silicon; b) Phonon dispersion relation for Hafnium